Construction of roads and ways



June 16, 1925.

R. J. M. LARRANAGA CONSTRUCTION OF ROADS AND WAYS F'iled Sept. 9, i922Patented June 16, 1925.

CONSTRUCTION DE Application filed September To all whom it mag"concern."

Be: it known that I, PETER Jo N MANUEL LARRASIAGA, a Peruvian citizen,residing in London, England, have invented certain new and usefulImprovements in or Relating to theConstruction of, Roads and \Vays, ofwhich the/following is a specification.

This invention relates to ,the paving of roads ilnflflSLllfttGBS. v v av Great difliculty has been experienced in constructing roads towithstand the stresses producedby modern traffic, more particularly thepounding orlimpact shocks-as diiferentiated fromthe static loadstressesq This is due inga greatvmanycases to the fact that either thematerials or method of construction or both, do'not permit the requisitecombination of V elasticity a and strength as in; the case of cementconcrete foundations and asphalt or wood wearingsurfaces, wherethehammering action of traliic crushes and destroys the wearingsurfaceagainst its inelastic rigid unyielding foundation, which acts as ananvil. Inother cases materials are used of such a nature and in such amanner as to permit elasticity, but the construction a whole is unableto resist the forces imposed and the ,surfacegives way by permanentyielding or deformation, as in corrugations. a n v Theobject of thepresent inventionis to overcome? the defects alluded to} above, and toprovide a road surface capable of resisting all the mechanical forcesimposed by the heaviest modern trafhc, as well as the physicah forcesdue to weather and other causes, without suffering any deterioration,

or-requiring any maintenance for anumber of years, a y

The present invention COIlSlSiZSJIItllQ production of a road structurein which are embedded and arranged one or more series of suitably formedelements offa greater rigidity than that of the structure surroundingthem. (The present invention also consists} in; the formation of suchelements of slabs ofvrigid material of suitable form and dimensionembedded in the surround ing structure, lying substantially flat,

spaced as desired, and either, unconnected,

Pnrrnn JOHN MANUEL LARRAFIAG or LONDON, ENGLAND.

noses Ann WAYS.

a, 1922. SeriaLNo. 587,201. a

or interconnected in any suitable manner, the slabs of each: seriesforming a continuousline of pressure and shockdistributing elements asthe sleepers of a railway track.

The accompanying drawing illustrates by way of example a suitableconstruction according to the invention. V y

In the drawing, Fig. 1, is a cross sectionalwiew of a paving constructedaccording to the invention, and a a Fig. 2 is a part sectional plan viewin perspective thereof. a u

,-Fig. 3 is a cross sectional View similar g. l but showingawearingsurface of wood blocks. p p n y 1. On any approved well drainedand compacted subgrade, which may bean old road: surfacer l, a course 2is laid, about two inches thick after compressiom-ofdense bituminousconcrete,, prepare-d of graded mineral aggregrate having a minimum ofvoids, and a bituminous binder, which may beeither pure bitumen, nativeasphalt," or tar, or compounds thereof, the binder to be of a softerconsistency than that generally used in the construction of an ezc posedwearing surface. p i 7 Thisbottom course 2 isthencompacted with a heavyroller, and the surface is pref erably left rough and open and nottreated with any surface flush coat of: bituminous material and stonechippings or sandas for an exposed wearing surface.

5 2. As soon as possibleafterthe prepare tion of the bottomcourse 2, amiddle course 3 about three inches thickis laid consist: ing of Portlandcement concrete slabs laid fiat, prepared and formed, either in situ, orpreviously to laying, care being taken to employ a mixture of aggregatescientificially graded to havethe minimum of voids and the greatestmechanical stability, if possible the same aggregate as used inthebottomcourse. The slabs 3 may be of any suitable dimensions and form, as forinstance six foot squares, and the edges may be of any desired. form orprofile either in plan view or-verticalsection. Thethickness or verticaldepth of a slab need not be uniform throughout, that is, the upper andlower surfaces need not be planes or parallel with each other, but themean thickness will always be small in dimension compared with thelength or breadth. The slabs are preferably spaced apart horizontally,say, by a distance of four to six inches, and, preferably, unconnectedexcept by the material 2 of the surrounding joints. These joints 4: arefilled flush to the upper surface of the slabs G with bituminous mixtureof a character similar to that used in the construction of the bottom.course 1t may be found convenient to build up the bituminous jointsfirst and utilize them as forms into which the cement concrete formingthe slabs may be poured.

The entire middle course 3 of cement concrete with bituminous joints 4is then rolled with a heavy roller, so as to secure maximum compressionand adherence to the bottom course. This middle course should not betrowelled but left rough and open, ready to receive and interlock withthe wearing course to be laid thereon.

3. \Vithout awaiting the setting of the concrete, but as soon as themiddle course has become reasonably dry, any standard wearing surfacecourse 5 is laid, as for instance of dense bituminous concrete about twoinches thick, sheet asphalt, wood block, or other selected type.

In Fig.- la wearing surface 5 of asphalt is shown and in Fig. 3 awearing surface 6 of wood blocks.

Any of the above three courses may be of such thickness as circumstancesmay call for.

The slabs maybe constructed in any manner and of any materials so as togive the requisite rigidity, and may be arranged in any suitable manner,as for instance in parallel longitudinal or transverse rows, laid so asto break joint, or not. They need not all be of the same size or form,and any number of layers of slabs if desired, may be laid and embeddedone on top of the other at a suitable depth apart.

It will be seen that the slabs being arranged between layers ofresilient bituminous mixture act as pressure and shock distributingelements from the upper to the lower portions of the road bed. This istheir main function. They form in some respects a series of rigidindependent elements similar to the vertebrae of a backbone, each beingfree to move slightly relatively to those adjacent thereto, and thuspermitting the full benefitof the general elasticity of the whole roadbed structure, and in particular of the lower portion, in efficientlywithstanding shocks. The rigid cement concrete slabs of the middlecourse cushion against the underlying bituminous concrete of the lowercourse, and the anvil-like character of a continuous course of cementconcrete, as used in common practice, is obviated.

It will also be llOtQt that the construction described permits a minimumuse of materials to produce an efiicient result, the total depth of theroad bed only amounting to some seven inches. Further all the materialsemployed are well known and easily obtainable.

lilaving thus described the nature of my 7 said invention and the bestmeans I know of carrying the same into practical eifect, I claim 1. Apaving consisting of a bottom layer of bituminous concrete, a middlelayer of concrete slabs spaced a substantial distance aparthorizontally, the spaces between said slabs being filled with'bituminousconcrete flush to the upper surface of said slabs, which locks themhorizontally, and a top wearing surface course; the whole having ageneral elasticity.

A paving consisting of a bottom layer of dense bituminous concrete, amiddle layer of concrete slabs spaced a substantial dis tance aparthorizontally, the spaces between said slabs being filled in withbituminous concrete, flush to the upper surface of said slabs, whichlooks them horizontally, and a top wearing surface course of bituminousconcrete, the whole having a general elasticity.

3. A paving consisting of a bottom layer of dense bituminous concrete, amiddle layer of concrete slabs spaced a substantial dis- 1 tance aparthorizontally, the spaces between said slabs being filled in withbituminous concrete, flush to the upper surface of said slabs whichlocks them horizontally, and a top wearing surface course of sheetasphalt, the whole having a general elasticity.

4-. A paving consisting of one or more layers of suitably formed rigidpressure and shock distributing elements, each spaced apart asubstantial distance horizontally from the adjacent element so that eachelement is capable of independent relative movement, the layer as awhole being flexible, said elements being contained between a lowerlayer of waterproof elastic material with which they are interlocked andan upper layer forming a top wearing surface course of substantialthickness which prevents the tratfic from making contact with thepressure and shock distributing ele- 1 0 ments.

5. A paving consisting of abottom layer of bituminous concrete, a middlelayer of Portland cement concrete slabs, spaced aparta substantialdistance horizontally, the 1 spaces between said slabs being filled inwith bituminous concrete to form a level surface and to lock the slabshorizontally, and a top wearing surface course of any usual material andof substantial thickness which prevents the traflic from making contactWith the concrete slabs, the Whole having a general elasticity.

6. A paving consisting of a bottom course of flexible resilientmaterial, an intermediate course supported by said bottom course andhaving a layer of flat relatively rigid slabs forming pressure and shockdistributing ele-

